Koa web app framework
Expressive HTTP middleware framework for node.js to make web applications and APIs more enjoyable to write. Koa's middleware stack flows in a stack-like manner, allowing you to perform actions downstream then filter and manipulate the response upstream.
Only methods that are common to nearly all HTTP servers are integrated directly into Koa's small ~570 SLOC codebase. This includes things like content negotiation, normalization of node inconsistencies, redirection, and a few others.
Koa is not bundled with any middleware.
Koa requires node v7.6.0 or higher for ES2015 and async function support.
$ npm install koa
const Koa = ;const app = ;// responseapp;app;
Koa is a middleware framework that can take 3 different kinds of functions as middleware:
Here is an example of logger middleware with each of the different functions:
// Middleware normally takes two parameters (ctx, next), ctx is the context for one request,// next is a function that is invoked to execute the downstream middleware. It returns a Promise with a then function for running code after completion.app;
To use generator functions, you must use a wrapper such as co that is no longer supplied with Koa.
Old signature middleware (v1.x) support will be removed in v3
Koa v2.x will try to convert legacy signature, generator middleware on
app.use, using koa-convert.
It is however recommended that you choose to migrate all v1.x middleware as soon as possible.
// Koa will convertapp;
You could do it manually as well, in which case Koa will not convert.
const convert = ;app;
For Node 4.0+ and Babel 6.0 you can setup like this:
$ npm install babel-register babel-plugin-transform-async-to-generator --save
// set babel in entry fileplugins: 'transform-async-to-generator';
Check out an example in koa's test.
$ make test